In recent years, in aim of enabling a higher breakdown voltage, a lower loss, and a use under a high-temperature environment for a semiconductor device such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), employment of silicon carbide as a material constituting the semiconductor device is now under way. Silicon carbide is a wide band gap semiconductor having a wider band gap as compared to silicon which has been conventionally and widely used as a material constituting a semiconductor device. Therefore, the employment of silicon carbide as a material constituting a semiconductor device can achieve a higher breakdown voltage and a reduced on-resistance of the semiconductor device. Moreover, a semiconductor device employing silicon carbide as a material has an advantage that lowering of the properties in the use under a high-temperature environment is smaller as compared to a semiconductor device employing silicon as a material.
For example, Brett A. Hull et al., “Performance of 60A, 1200V 4H—SiC DMOSFETs”, Materials Science Forum, Vols. 615-617, 2009, pp 749-752 (NPD 1) discloses a MOSFET which has an n-type drift region, a pair of well regions, and a gate insulating film formed on a silicon carbide substrate. The document described above discloses that a value of a specific on-resistance of the MOSFET is 9 mΩcm2 at VGS=20V.